The invention relates to a regulation method for regulating the temperature in a reactor utilized in the polymerization of olefines, in which method a circulating gas is led to the reactor along a circulating gas flow line. The circulating gas is cooled by leading the circulating gas through a cooler before it enters the reactor.
In the methods known from prior art, the circulating gas is led to the reactor via a straight pipe line provided with a cooler. This known regulation method is extremely slow, because the temperature of the circulating gas can not rapidly be changed.